1. Field of the Invention
This invention relates to a rotation transmitting mechanism in which a shaft rotates in the fixed direction irrespective of the direction of rotation of another shaft.
2. Description of the Related Art
A kind of apparatus in which an output shaft is driven in the fixed direction irrespective of the direction of rotation of an input shaft is known as, for example, feed tables for machine tools. Ordinarily, in this apparatus, a rotation transmitting mechanism for reverse rotation is interposed between the feed table and a main shaft, and the direction of the rotation transmitted to the feed table is changed over by the rotation transmitting mechanism if the direction of rotation of the main shaft is changed by following a driving unit separately provided.
Conventionally, mechanisms based on the combination of gears are generally used as this kind of rotation transmitting mechanism. For example, a drive gear is provided on an input shaft of a rotation transmitting mechanism to mesh with a driven gear fixed to an output shaft. As the input shaft connected to a driving source such as a motor is rotated counterclockwise, the output shaft is rotated clockwise and opposite to the rotation of the input shaft through the drive gear and the driven gear. The drive gear is axially slidable on the input shaft by the function of, for example, a slide key, and meshes with an intermediate gear provided on an intermediate shaft when axially moved. The intermediate gear meshes with another driven gear disposed on the output shaft parallel to the former driven gear. The rotation of the input shaft is transmitted to the output shaft through the drive gear, the intermediate gear and the latter driven gear, thereby rotating the output shaft counterclockwise in the same direction as the input shaft. That is, it is possible for the rotation transmitting mechanism to change over the direction of rotation of the output shaft by artificially sliding the drive gear on the input shaft. Accordingly, even if the rotation of the motor provided as the drive source is reversed according to the direction of rotation of the other connected drive unit, the output shaft can be rotated in the same direction as previous by changing over the drive gear.
In this type of conventional rotation transmitting mechanism, however, there is a need for the operation of changing over the drive gear according to the direction of rotation of the drive source as well as a need for providing the changeover mechanism having a complicate structure. This rotation transmitting mechanism therefore entails the problem of the operation being complicated and inconvenient as well as the problem of increase in the production cost. Moreover, because the rotation is transmitted through gear, it cannot be smoothly transmitted owing to backlashes between the gears when the rotation is reversed.